With the advent of high energy costs, especially fuel for fuel burning furnaces for home heating applications, the loss of energy through the exhaust stack during the non-heating cycle of the furnace has been recognized as a major energy loss. While furnace stack damper control apparatus in many forms has been known for some time, the safety aspect of such apparatus has somewhat deterred past use of such apparatus. While many different types of control circuits for such apparatus are known, there has always been a need for a more reliable and safe circuit as the failure of such a stack damper control apparatus on a furnace can result in the confinement of fuel combustion products in a house resulting in a hazardous condition to the occupants.